Z-value

An index of the ionizing power of a solvent based on the frequency of the longest wavelength electronic absorption maximum of 1-ethyl-4-methoxycarbonylpyridinium iodide in the solvent. The Z-value is defined by:

$Z = 2.859 × 10 4 λ$

where $Z$ is in $kcal mol −1$ and $λ$ is in $nm$ .

See also: Dimroth–Reichardt $E T$ parameter, Grunwald–Winstein equation

Source:

PAC, 1994, 66, 1077 (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1176